1. Field of the Invention
The present invention refers to a method for depositing a layer at a substrate wherein the layer contains at least two components provided by at least two evaporation sources. Moreover, the present invention refers to an apparatus for depositing such a layer.
2. Prior Art
The use of evaporation sources for producing thin film layers for an organic electroluminescence element is known from EP 1 197 576 A1 or EP 1 078 999 A2. According to this prior art, two or more materials are deposited by a vacuum evaporation. When the two or more materials are simultaneously deposited, to form a layer, a mixture of the components or doping of the layer is achieved. Thus, dopants may be deposited simultaneously with an organic material to form organic layers of an organic light emitting device OLED or an organic photovoltaic device.
EP 1 197 576 A1 describes a method to achieve a homogeneous deposition layer having only small variations in the density of each of the materials, even if large area substrates are coated. This is achieved by adjusting the shape of the crucible of the evaporation sources as well as changing the evaporation rates according to a specific formula.
EP 1 078 999 A2 also describes a system and a method for fabricating organic electroluminescent display devices. Again, highly homogeneous layers with respect to film thickness distribution as well as a constant doping concentration shall be achieved. The solution suggested by EP 1 078 999 A2 comprises usage of a specific rotation system where the substrate is rotated by rotation means during deposition. With respect to such a deposition system, the position of the evaporation source is defined, to achieve the above-mentioned objects. Moreover, it is disclosed that the evaporation sources may be tilted to achieve a satisfactory film thickness distribution for the given rotation evaporation method.